Among the questions confronting developmental visual scientists are the relative sequences of development of projection neurons and interneurons in visual centers and the diferentiation of the neurotransmitter systems used by these neurons and interneurons in visual centers and the differentiation of the neurotransmitter systems used by these neurons. The methods currently available are insufficient to resolve these and related problems. Therefore, this project proposes to develop two new techniques which will provide direct evidence regarding such issues. The rat visual cortex will be used as a model. 1. A combined tritiated thymidine authoradiographic Golgi procedure will be used to assess possible differential maturation of cortical pyramidal and non-pyramidal neurons. Processed tissue will be analyzed for double-labeled neurons - one label being silver grains over nuclei (designating those cells "born" on the day of injection) and the other label being the Golgi deposit (Which labels the dendrites cell body and axon of morphologically identified pyramidal and non-pyramidal neurons). 2. The morphology of non-pyramidal neurons using particular putative neurotransmitter(s) will be determined using a combine autoradiographic-immunocytochemical-Golgi procedure. This will rely on direct correlation of labeling of the same neuron in serial sections. These procedures will provide valuable pilot data and create new approaches to investigating current questions in developmental neurobiology. Furthermore, these techniques will be applicable to studies of synaptogenesis and the effects of visual experience on neuronal development.